问题
I've been getting some java.lang.OutOfMemoryError: GC overhead limit exceeded errors while running my Java app overnight:
java.lang.OutOfMemoryError: Java heap space
Dumping heap to java_pid6376.hprof ...
Heap dump file created [512149941 bytes in 23.586 secs]
23:34:52,163 WARN [HDScanner] Scan failed
java.lang.OutOfMemoryError: Java heap space
23:34:52,298 ERROR [ContainerBase] Exception invoking periodic operation:
java.lang.OutOfMemoryError: Java heap space
23:34:52,321 ERROR [JIoEndpoint] Socket accept failed
java.lang.OutOfMemoryError: Java heap space
at java.net.ServerSocket.accept(Unknown Source)
at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:61)
at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:310)
If I open up jvisualvm, I can see that I am indeed out of heap space:
I'd like to profile it to try to figure out what's going on - is there a memory leak? etc. However, I'm unable to get the jvisualvm profiler to do anything at all. The Profiler tab shows a warning about class sharing being enabled:
...even though I've added the -Xshare:off flag to my VM args:
So,
- Any ideas about how to get profiling to work?
- Is it worth playing around with G1GC instead of ...whatever GC I'm currently using?
回答1:
It looks to me that you are running VisualVM on 32-bit JVM and your JBoss is running on 64-bit JVM. In such situation profiler and other things like Threads and CPU monitoring does not work on Windows out of the box. With profiler you are running into bug #273, where profiler is incorrectly enabled. You should do the following:
- Dowload latest 64-bit JDK (currently JDK 6u23). It also contains the latest version of Java VisualVM
- Use memory sampler in VisualVM (it has much lower overhead than profiling) to see if you can spot the problem.
- If that does not help, take a look at the heap dump and try to find out what is going on.
- Do memory profiling of your JBoss server. See Profiling With VisualVM, Part 1 and Profiling With VisualVM, Part 2 for more information about profiler in VisualVM.
来源：https://stackoverflow.com/questions/4660334/unable-to-profile-jboss-5-using-jvisualvm